This invention relates to conduit joints. More particularly the invention relates to an improved slip joint and method of making same.
There are many types of tube joints which are in common use in tube systems. One of the most common, referred to as a slip joint, is made by slipping the straight male end of one piece of tubing into the expanded female end of another. It is ordinarily desirable to avoid sharp edges along the inner surfaces of such tubing since such edges disrupt fluid flow or, where such tubing is used to pneumatically transport capsules, the edges tend to scrape and/or tear at the capsules passing thereby. To avoid sharp edges in conventional slip joints, the inside of the male end is deburred and chamferred with a hand file, a very time consuming and expensive operation. It is also difficult to control the quality of a handmade joint such as this. Alternatively, a reamer may be used to chamfer the inner edge but such practice requires subsequent hand filing to remove burrs and therefore is of little advantage over hand chamfering.
Another type of joint in common use is a butt joint, usually with some sort of sleeve slipped over the outside. Here it is necessary to deburr both ends, with the attendant disadvantages discussed above. Another disadvantage of a butt joint is that if one of the tubes is oval in a direction not coincided with the ovality of the other, it can be very difficult to obtain a good, smooth joint. Such ovality is common where tubing is cut.
Yet another disadvantage attendant with both of the above joints is that in deburring or chamfering the inner surface of the tubing the galvanized finish is removed, thus leaving the conduit susceptible to corrosion which causes joint roughness, and eventually leakage.